178 
FXUS61 KBUF 090906
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
506 AM EDT Sun Aug 9 2020

.SYNOPSIS...
An area of high pressure over the Ohio Valley today will drift 
to the Eastern Seaboard by Monday. This will provide mainly dry 
conditions through the start of the new work week, although a 
few weak upper level disturbances crossing the region may bring 
a few showers from time to time, especially across northern 
areas. A weak cold front will then cross the region on Tuesday, 
bringing the next chance for more widespread showers and 
thunderstorms. Otherwise, temperatures will remain above normal 
through the upcoming week.

&&

.NEAR TERM /THROUGH TONIGHT/...
The typical valley fog across the Southern Tier will lift out by mid 
morning.

An area of surface high pressure will reside across the Ohio Valley 
today, providing the bulk of the area with dry weather. However, an 
upper level trough moving down the Ottawa Valley this morning, will 
cross northern NY this afternoon. This will keep the bulk of the 
scattered showers and storms associated with this feature to the 
north of Lakes Erie and Ontario across southern Ontario Province. 
However, as upper level energy moves across northern NY this 
afternoon, there will be the chance for a few showers and storms for 
areas east of Lake Ontario into the Saint Lawrence Valley during the 
second half of the day. Southwest winds will increase with the 
approach of the trough, with gusts of 20-30 mph northeast of Lakes 
Erie and Ontario in the afternoon as the surface pressure gradient 
tightens and somewhat stronger winds off the deck mix down to the 
surface. Otherwise, temperatures will nudge upward another degree or 
two today, with highs in the lower to mid 80s across the majority of 
the area.

A few showers/isolated storms may linger east of Lake Ontario 
through late this evening as the upper level trough exits east of 
the area. The next weak shortwave will cross the area during the 
second half of the night, renewing the chance for a few more showers 
and storms from the Niagara Frontier east and northeast to the 
eastern Lake ontario region as this feature interacts with a subtle 
weak warm front lingering from central Lake Ontario into Central NY. 
With little in the way of precip, or even cloud cover for that 
matter across the Southern Tier, may see another night with typical 
valley fog. Low temperatures tonight will be much warmer than 
previous nights, as readings will likely only fall back into the mid 
and upper 60s across the bulk of the area, with lower 60s found 
across the higher terrain.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A subtle warm frontal boundary will be draped over and southeast of 
Lake Ontario Monday morning, with a convectively augmented mid level 
shortwave also moving southeast across the area. Weak moisture 
convergence near the warm front and forcing from the shortwave may 
support a few scattered showers and storms Monday morning over and 
southeast of Lake Ontario, with this activity then drifting east 
during the afternoon. A few more isolated showers and storms may 
develop along and inland of the lake breeze boundaries Monday 
afternoon, but the majority of the area will stay dry. Temperatures 
will continue their day to day rise, with highs in the upper 80s to 
around 90 at lower elevations away from lake influences. Dewpoints 
will also climb into the upper 60s to around 70. This will translate 
into a heat index in the 90-95F range. The most probable location of 
marginal heat advisory criteria (95F) is from the Genesee Valley 
eastward through the western Finger Lakes to Oswego County.

Any isolated diurnal showers and storms will dissipate Monday 
evening, leaving dry weather overnight. A very warm/muggy airmass 
and southwest breeze will not allow temperatures to fall much, with 
lows in the lower 70s on the lake plains and mid 60s across the 
interior Southern Tier and Lewis County.  

Tuesday and Tuesday night a weak mid level trough and associated 
cold front will approach the area. 00Z model guidance continues to 
trend slower with this feature, not bringing the cold front through 
the eastern Great Lakes until very late Tuesday night or Wednesday 
morning. Tuesday will start dry, with scattered showers and storms 
developing in the afternoon along lake breeze boundaries and a pre-
frontal trough. The scattered showers and storms will continue 
Tuesday night as the mid level trough and cold front cross the area. 
PWAT values climb to around 1.75 inches, so any storms will be 
capable of very heavy downpours. Relatively weak shear and poor mid 
level lapse rates will limit the severe weather risk. Tuesday will 
be another very warm and humid day, with highs in the mid 80s across 
Western NY and around 90 from the Genesee Valley eastward at lower 
elevations. The heat index may again reach 95 from the Genesee 
Valley to the western Finger Lakes and Oswego County.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
The cold front moving through the area late Tuesday night and 
Wednesday morning will lay out in an east-west orientation from the 
Ohio Valley to PA Wednesday, and stall in place through the end of 
the week. Several weak, convectively augmented waves will move 
eastward along the front, providing periods of enhanced ascent and 
moisture convergence. If a stronger frontal wave materializes it may 
also modulate the frontal position. 

The GFS/GEFS mean remains on the northern side of the guidance 
envelope, with the ECMWF/GEM keeping the front and associated 
sensible weather well south of the area. Given the emerging 
ECMWF/GEM consensus of a farther south solution, lowered POPS 
Wednesday through Friday with a dry forecast for the majority of the 
area and low chance POPS over the Southern Tier. By Saturday deeper 
moisture, instability, and forcing may begin to creep back northward 
as the next trough moves into the Upper Midwest, bringing a chance 
of a few scattered showers and storms.

Temperatures will continue to run above average Wednesday through 
next weekend despite being to the north of the stalled frontal zone. 
Expect highs in the mid 80s at lower elevations each day, with lows 
in the 60s. Dewpoints will remain somewhat lower to the north of the 
boundary, keeping humidity relatively comfortable.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
Typical river valley fog will impact the Southern Tier through mid 
morning with local IFR conditions.

Mid and upper level clouds will be found across the area today, with 
some low VFR decks east of Lake Ontario during the second half of 
the day, where a few showers and storms will be possible as well 
this afternoon/evening. Otherwise, it will be mainly dry with VFR 
flight conditions area wide through this evening.

Outlook... 

Sunday night through Monday...Mainly VFR. A small chance of showers. 
Tuesday...Showers and thunderstorms likely. Brief MVFR/IFR possible. 
Wednesday and Thursday...Mainly VFR with an afternoon/evening shower 
or thunderstorm possible.

&&

.MARINE...
A tightening pressure gradient will allow southwest winds to 
increase on both lakes today ahead of a weak upper level trough. 
This will produce choppy conditions on Lake Erie. Winds will be a 
bit lighter on Lake Ontario, but still enough to generate some chop, 
especially across the western half of the lake.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...JM
NEAR TERM...JM
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...JM
MARINE...JM